1. Field of the Invention
The present invention relates to an agricultural device. The agricultural device is configured to couple an agricultural implement to a tractor vehicle. The tractor vehicle has carrier arms. The agricultural device is couplable only to the carrier arms of the tractor vehicle, in order to transmit tensile forces. The agricultural device serves as an auxiliary device for the coupling of at least one agricultural implement. The agricultural implement is for example a tedder or a mower. The agricultural device comprises a carrier frame extending in the longitudinal direction, for example a drawbar, with a set of wheels and a coupling device at the first end. The agricultural implement can be coupled to the agricultural device via the coupling device, so that the agricultural implement is located behind the agricultural device. The agricultural implement can also be held in a working and raised position with the aid of the coupling device. The raised position can for example be used as a headland position or transport position. The assembly made up of the agricultural device with the agricultural implement can be coupled to the tractor vehicle.
At a second end, the agricultural device has a coupling frame for coupling of the agricultural device to the tractor vehicle. The coupling frame can be connected to the carrier frame so as to be hingeable about an upward axis of rotation. The coupling frame has at least one coupling point for coupling to the carrier arms of the tractor vehicle. The agricultural device can further comprise a drive coupling shaft with a centre line so as to allow the agricultural implement to be coupled to the drive shaft of the tractor vehicle. The drive coupling shaft extends from the coupling frame up to the coupling device.
2. Description of the Related Art
The tractor vehicle is equipped with carrier arms for the coupling. DIN 9674, which is hereby incorporated by reference in its entirety, describes in a standard for agricultural tractors and machines a three-point coupling with two carrier arms and a top link. The two carrier arms and the top link each have a free end for the coupling of the agricultural device. The two carrier arms are hingeably fastened below a drive shaft. The free ends of the carrier arms are movable from a position below the drive shaft to a position above the drive shaft. The carrier arms of the three-point coupling can be driven in order to move a load upwards or downwards. The invention relates to a coupling of the agricultural device to the tractor vehicle wherein no use is made of the top link.
Usually, the carrier arms can be energized only upwards using a hydraulic cylinder in order to carry the load, for example an agricultural implement. The hydraulic cylinder has a piston which is movable back and forth. A hydraulic fluid is located below the piston. Air is located above the piston. The piston can be moved upwards by increasing fluid pressure below the piston. Owing to the load on the carrier arms, the piston will fall again as the fluid pressure drops.
The known carrier arms have the problem that, after the carrier arms have been brought into an intermediate or low position, the piston can continue to move upwards. That is to say, in the event of an upward force on the carrier arms, the piston in the cylinder can move upwards, wherein merely air resistance has to be overcome. Upward forces can occur as a result of the towing of the agricultural device. As a result, the carrier arms can move from a lower position upwards to an intermediate position, wherein the carrier arms enter a substantially horizontal position. The prior art usually provides a top link in order to hold the carrier arms in a low position during the towing of the agricultural device. If the top link is not present in the coupling of the agricultural device to the tractor vehicle, there is therefore the risk that the carrier arms will rise in an unexpected and undesirable manner. This upward movement of the carrier arms can occur at unexpected moments. This can give rise to dangerous situations during tillage on the ground when heavy components unexpectedly start to move. Furthermore, damage can occur to the tractor vehicle or to the coupled agricultural implement.
The undesirable upward movement of the carrier arms is particularly important when an agricultural implement is coupled to the tractor vehicle behind the set of wheels of the agricultural device described hereinbefore. When the agricultural implement is brought into the raised position, the agricultural device can tilt over the set of wheels and an upward force is produced acting on the carrier arms. This can cause the carrier arms to move upwards, wherein the carrier arms can come to a halt with a bang in an extremely high position. Apart from the fact that this can lead to dangerous situations and damage, a further drawback is the fact that the upward movement of the carrier arms and the accompanying upward hinging of the carrier frame also ensures a downwardly directed movement of the agricultural implement. This can result in an excessively low arrangement of the agricultural implement in a transport position, as a result of which the agricultural implement can become damaged during transportation owing to collisions with the ground.